1. Field of the Invention
The present invention relates to a C/C composite material precursor, a C/C composite material, and a method for producing the C/C composite material.
2. Description of the Related Art
A C/C composite material (also referred to as “carbon/carbon composite material” and “carbon fiber reinforced carbon composite material”), which is one of composite materials formed of carbon fiber and a carbon matrix, has high specific strength and high specific rigidity for all its lightness in weight, and still has high strength even at a high temperature of 2,000° C. It is widely used in fields where reduction in weight is demanded, such as field of automobile and field of aerospace.
Such a C/C composite material is produced by, for example, laminating a predetermined number of prepregs (in FIG. 9, five prepregs 111A, 111B, 111C, 111D and 111E), subjecting the lamination to heat treatment to thereby obtain a C/C composite material precursor (carbon fiber reinforced plastic (CFRP) shaped body), and then subjecting to calcination (see Kokai Unexamined Japanese Patent Publication No. H2-124765, page 3, left column, line 10-page 4, left column, line 1).
In the case of a thick C/C composite material, such as one having a thickness of 30 mm or more, it is produced by laminating prepregs to form a element piece having a thickness of 25 mm or less, applying a mixture of phenolic resin and graphite powder between two element pieces to thereby adhere the element pieces, subjecting the adhered element pieces to hot pressing for curing the mixture to thereby obtain an intermediate, and then subjecting the intermediate to calcination (see Kokai Unexamined Japanese Patent Publication No. 2002-264744, paragraph 0007 and FIG. 3).
Generally, gas is generated by volatilization or decomposition of a matrix (substrate made of synthetic resin) of the prepeg during calcination. In the case of the method disclosed in the above document Kokai No. H2-124765, generated gas is trapped in the C/C composite material and may expand. Such gas may further combine with other gas trapped in the vicinity, leading to causing fissures 103 along the interface between two adjacent layers of the C/C composite material 101 and to separating the laminated layers, as shown in FIG. 10. It should be noted that the layers shown with the reference characters 101A, 101B, 101C, 101D and 101E in FIG. 10 correspond to the above-mentioned prepregs 111A, 111B, 111C, 111D and 111E, respectively.
To solve the above-mentioned problem, a trial has been made to prevent the layer separation in which production conditions, such as temperature and period of calcination, are properly controlled so as to gradually generate gas. However, the conditions have to be properly adjusted in accordance with provided various factors, such as thickness and material of prepreg, the number of prepreg sheets to be laminated and the amount of generated gas. As a result, it takes time and effort to produce a C/C composite material.
Likewise, in the method disclosed in the above document Kokai No. 2002-264744, more steps are required in which the intermediate is manufactured and then subjected to calcination, which also requires time.
Therefore, it would be desirable to provide: a C/C composite material precursor that facilitates production of a C/C composite material; a C/C composite material; and a method for producing the C/C composite material.